The Question: How many slides for a 30/20/10 or 5 minute presentation?
The Answer: It does not matter. Have the right content, say one thing per slide and finish before the allotted time. Do not worry how many slides your presentation runs into. Read the detailed answer here.
But I will still give you a ball park number. Normally in the business presentations I have seen in my career, the presenter spends two to three minutes per slide. Hence,
No. of slides = (No. of minutes) / 2
It is better to have lesser no. of slides and finish before than to exceed time. By finishing early you also get more time for question and answers.
Even if you realize that there is no ideal number there are various reasons which will make you worry about the original question. This is something I want to discuss in today's post. The reasons why you are forced to think on the number of slides?
Concern #1: Printing handouts. Lesser number of slides means lesser number of prints.
Concern #2: Time management. If I have more slides I will exceed the time
Answer #1: If you are going to present more slides then you need more prints. This might make your handout bulky and will have lesser content on each page. Looks like waste of space right? Wrong! You should never print slides and give it as handouts in the first place. A handout should be prepared separately and should capture the main points of your presentation. Why print something which cannot stand alone without your presence. Read more on handouts here.
Answer #2: Time management is the main concern why people want to know how many slides is right. You can manage time by planning like this: If you have three sections in your presentation and 30 minutes, then first decide on how many minutes should you spend behind each section. If you allocate 10 minutes for section 1 then ask yourself, "How much content should I share with my audience so that i finish within 10 minutes?".
The presentation content is your input (leading indicator) and the no. of slides is your output (lagging indicator). To manage time, focus on the input that goes into the presentation and not the output.
Once you have zeroed-in on the right content it all depends on your presentation style. If you present visuals and want small bits of information per slide then you might run into many slides. If you are putting up complex information (a table for example) and want to elaborate on it, then just 2/3 slides might take up 10 minutes.
The bottomline is, do not worry on the number of slides. Know how much time you have and decide on how much information can you share within that time. How does it matter if your presentation has 10 slides or 20?
It's not over yet. To end today's post let me ask you something. Arvind, a sales manager, has to make a 20 minute presentation in his office and his boss has put a upper cap of 5 slides. Arvind does not feel that he can 'put' all the content in just 5 slides. What should he do? How can he put 10 slides' matter into 5? How can he circumvent the law without breaking it?
Update (Sept 2013)
-----------Check out this link. I have written a small post about it.
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